Retaining walls can be constructed in a conventional way from a suitable concrete mix poured into requisite forms mounted on footings which, upon curing and removal of the forms and after suitable trimming and smoothing over of the rough edges and surfaces, are backfilled and landscaped to complete the job. Such an approach provides a very strong and durable structure but is time-consuming and costly normally requiring skilled labour and heavy commercial equipment to undertake and complete the project.
It is also common practice to construct a retaining wall from precast concrete slabs or from trimmed rock slabs or rock pieces mounted upon suitably prepared footings. The slabs or pieces can be of a size and weight sufficient in themselves to maintain the wall profile. Mortar can be used to anchor the slabs or rock pieces in place. Such proposal is likewise time-consuming and expensive, normally requiring skilled labour to achieve acceptable standards.
Interlocking precast concrete stretchers or slabs and headers have been produced and used to build suitable retaining walls and cribbing in which mortar is not required except for securing the top or coping block or stretcher or slab against dislodgement and in relation to which skilled labour is required only in the initial phases to establish the requisite base for such structure and for trimming the slab lengths and corners.
Such structures are described and illustrated in the following patents:
______________________________________ U.S. Pat. No. 847,476 U.S. Pat. No. 1,248,070 U.S. Pat. No. 1,733,790 U.S. Pat. No. 1,773,579 U.S. Pat. No. 1,787,200 U.S. Pat. No. 1,907,053 U.S. Pat. No. 2,034,851 U.S. Pat. No. 2,094,167 U.S. Pat. No. 2,197,960 U.S. Pat. No. 2,313,363 U.S. Pat. No. 2,371,201 U.S. Pat. No. 2,972,870 U.S. Pat. No. 3,488,964 U.S. Pat. No. 3,631,682 U.S. Pat. No. 3,877,236 U.S. Pat. No. 4,175,888 U.S. Pat. No. 4,190,384 U.S. Pat. No. 4,193,718 U.S. Pat. No. 4,229,123 U.S. Pat. No. 4,278,364 U.S. Pat. No. 4,314,431 Canadian Patent 941,626 German Patent 1,811,932 German Patent 2,755,833 German Patent 2,817,549 ______________________________________ It is to be noted in connection with the precast concrete stretcher and header structures of certain of the aforementioned patents that although the retaining walls to be constructed require only a shallow excavation for a footing where loads are substantial in circumstances wherein the structure will have a substantial height, skilled labour is required in preparing the footings and the laying of the first course of stretchers and headers because they must be disposed at a selected angle to the horizontal in order to establish the requisite degree of inclination of the retaining wall or cribbing. This inclination is essential to preserve the long term stability of the structure and to meet governmental regulations concerning safety.
Treated wooden logs are widely used in the construction of retaining walls or structures such as stairways and in cribbing in the landscaping of both commercial and domestic properties. This alternative while aesthetically pleasing, requires skilled labour. Moreover, treated wooden log structures are more costly than the equivalent precast concrete block or rock slab installation and tend to show damage by splitting through abrasion and by disintegration.